you want the most meat where the greatest forces are. (the back of the strut.) And the more the power, the more the forces are at that back. And trust me, you want meat there! Also, making an angle can create sharp edges where a crack can begin.
With that being said, I won't let one of my boats go in the water with a squared off back of the strut. But I won't shape it like the front. Just a little to help the water pattern recover before the propeller.